commit f531c57c7f67d72a597e3299a9cb2ec053d58d8d Author: juga0 juga@riseup.net Date: Wed May 20 13:44:59 2020 +0000

fix: doc: Add differences between Torflow and sbws

Closes #33871. --- docs/source/torflow_aggr.rst | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+)

diff --git a/docs/source/torflow_aggr.rst b/docs/source/torflow_aggr.rst index 10b12a8..5b4b3fd 100644 --- a/docs/source/torflow_aggr.rst +++ b/docs/source/torflow_aggr.rst @@ -385,6 +385,42 @@ Per relay scaled bandwidth rounding Finally, the new scaled bandwidth is expressed in kilobytes and rounded a number of digits.

+Differences between Torflow aggregation and sbws scaling (May 2020) +------------------------------------------------------------------- + +Torflow does not exclude relays because of having "few" measurements or "close" +to each other for that relay. + +If there are not new measurements for a relay, Torflow uses the previous +calculated bandwidth, instead of the new value:: + + # If there is a new sample, let's use it for all but guards + if n.measured_at > prev_votes.vote_map[n.idhex].measured_at: + + [snip] + + else: + # Reset values. Don't vote/sample this measurement round. + n.revert_to_vote(prev_votes.vote_map[n.idhex]) + +The oldest measurements Toflow seems to take are from 4 weeks ago, while sbws +oldest measurements are 5 days old:: + + GUARD_SAMPLE_RATE = 2*7*24*60*60 # 2wks + + [snip] + + MAX_AGE = 2*GUARD_SAMPLE_RATE + + [snip] + + # old measurements are probably + # better than no measurements. We may not + # measure hibernating routers for days. + # This filter is just to remove REALLY old files + if time.time() - timestamp > MAX_AGE: + + .. _README.spec.txt: https://gitweb.torproject.org/torflow.git/tree/NetworkScanners/BwAuthority/R... .. _PID Controller: https://en.wikipedia.org/wiki/PID_controller .. _SQLSupport.py: https://gitweb.torproject.org/pytorctl.git/tree/SQLSupport.py#n493